Refractory sporotrichosis due to Sporothrix brasiliensis in humans appears to be unrelated to in vivo resistance

Drug Repurposing: Research Progress of Niclosamide and Its Derivatives on Antibacterial Activity

The development of antibiotic resistance complicates the treatment of infectious diseases and is a global public health threat. However, drug repurposing can address this resistance issue and reduce research and development costs. Niclosamide is a salicylanilide compound approved by the Food and Drug Administration (FDA), and it has been used clinically for treating parasitic infections for many years. Recent studies have shown that niclosamide can inhibit bacterial and fungus activity by affecting the quorum sensing system, biofilm formation, cell membrane potential, and other mechanisms. Here, we discuss recent advances in the antimicrobial applications of niclosamide and its derivatives to provide new perspectives in treating infectious diseases.

Beyond conventional approaches: Enhancing photodynamic therapy for refractory feline sporotrichosis caused by Sporothrix brasiliensis

Male cat, 2 years old, with a refractory infection by Sporothrix brasiliensis, presents a single nodular lesion in the left auricular pavilion. To confirm the diagnosis, cytology, fungal culture, antifungal susceptibility test, molecular analysis, and, to aid in the differential diagnosis, bacterial culture, antibiogram, and histopathology of the lesion were performed. In the absence of therapeutic success with conventional antifungals, photodynamic therapy (PDT) was introduced, demonstrating a satisfactory response in the sixth treatment session.

Emergence of zoonotic sporotrichosis due to Sporothrix brasiliensis in Minas Gerais, Brazil: A molecular approach to the current animal disease

Sporotrichosis is a neglected fungal zoonosis with significant impacts on human and animal health. Accurate diagnosis, treatment, and understanding of the transmission dynamics of Sporothrix species are essential for mitigating the spread of sporotrichosis. This study aimed to identify the Sporothrix species involved in the ongoing outbreaks of animal sporotrichosis in the metropolitan region of Belo Horizonte, Minas Gerais, Brazil, and analyse the phylogenetic relationships between pathogenic species to investigate the outbreak origin. Additionally, to better understand the evolution of the disease, we conducted a retrospective survey of positive feline and canine cases from November 2017 to July 2021 with proven cultures for Sporothrix. A significant increase in animal cases over the last 4 years was observed, with cats being the most affected host. Sporothrix brasiliensis was the predominant agent in 100% of the clinical isolates (n = 180) molecularly identified. Phylogenetic and haplotype analysis points towards the cases isolated from Minas Gerais sharing the haplotype originating from a long-lasting outbreak of cat-transmitted sporotrichosis in Rio de Janeiro, however, with a secondary contribution from genotypes circulating in other outbreaks in Brazil. Thus, we present clear evidence of the circulation of different S. brasiliensis genotypes associated with animal sporotrichosis in the metropolitan region of Belo Horizonte. Genetic monitoring can contribute to understanding the causal agent for zoonotic sporotrichosis in epidemiological processes and help to implement disease prevention and control measures.

Sporotrichosis in Argentina: clinical and epidemiological analysis

Introduction

Sporotrichosis is an implantation mycosis caused by Sporothrix spp. It is distributed worldwide and can be found in vegetation and soil. The most frequent route of infection is by trauma with elements contaminated with fungal propagules. Since domestic cats are the most affected animals and can transmit this infection to humans, sporotrichosis is considered a zoonosis. Clinical presentations include nodular lymphangitis, fixed cutaneous, pulmonary (rare), and disseminated (exceptional).

Objectives

To analyze the epidemiology of sporotrichosis in Argentina during 2010 and 2022. To describe the clinical presentation, diagnostic methods, and treatment of cases diagnosed during this period. To know the circulating genotypes and to observe possible associations with the geographic location where the infection was acquired.

Materials and methods

Analytical, retrospective, and observational study. We analyzed the medical records of patients with sporotrichosis from 12 health institutions in Argentina, between 2010 and 2022.

Results

We present 54 cases in which the most frequent clinical form was nodular lymphangitis, and the treatment of choice was itraconazole. Conventional diagnosis was made in all cases. Culture of clinical samples was more sensitive than direct examination because it allowed the isolation of Sporothrix spp. in all 54 cases. Molecular identification was performed in 22 cases, with Sporothrix schenkii sensu stricto being the most frequently isolated species.

Conclusions

This study allowed to know the epidemiology of this mycosis in Argentina, as well as the availability of diagnostic methods and the treatment of choice.

Single nucleotide polymorphisms and chromosomal copy number variation may impact the Sporothrix brasiliensis antifungal susceptibility and sporotrichosis clinical outcomes

Feline-transmitted sporotrichosis has garnered attention due to the recent high incidence and the lack of efficient control in the epicenter of the epidemic, Rio de Janeiro, Brazil. Sporothrix brasiliensis is the major pathogen involved in feline-to-human sporotrichosis in Brazil and displays more virulent genotypes than the closely related species S. schenckii. Over the last two decades, several reports of antifungal-resistant strains have emerged. Sequencing and comparison analysis of the outbreak strains allowed us to observe that the azole non-wild-type S. brasiliensis strain CFP 1054 had significant chromosomal variations compared to wild-type strains. One of these variants includes a region of 231 Kb containing 75 duplicated genes, which were overrepresented for lipid and isoprenoid metabolism. We also identified an additional strain (CFP 1055) that was resistant to itraconazole and amphotericin B, which had a single nucleotide polymorphism in the tac1 gene. The patients infected with these two strains showed protracted clinical course and sequelae. Even though our sample size is modest, these results suggest the possibility of identifying specific point mutations and large chromosomal duplications potentially associated with antifungal resistance and clinical outcomes of sporotrichosis.

Sporotrichosis Caused by Non-Wild Type Sporothrix brasiliensis Strains

The zoonotic transmission of sporotrichosis due to Sporothrix brasiliensis occurs largely in Rio de Janeiro state, Brazil since the 1990´s. Most patients infected with S. brasiliensis respond well to itraconazole or terbinafine. However, a few patients have a slow response or do not respond to the treatment and develop a chronic infection. The aim of this study was to analyze strains of S. brasiliensis against five different drugs to determine minimal inhibitory concentration distributions, to identify non-wild type strains to any drug evaluated and the clinical aspects of infections caused by them. This study evaluated 100 Sporothrix spp. strains obtained from 1999 to 2018 from the Evandro Chagas National Institute of Infectious Diseases, Fiocruz, which were identified through a polymerase chain reaction using specific primers for species identification. Two-fold serial dilutions of stock solutions of amphotericin B, itraconazole, posaconazole, ketoconazole and terbinafine prepared in dimethyl sulfoxide were performed to obtain working concentrations of antifungal drugs ranging from 0.015 to 8.0 mg/L. The broth microdilution reference method was performed according the M38-A2 CLSI guideline. All strains were identified as S. brasiliensis and thirteen were classified as non-wild type, two of them against different drugs. Non-wild type strains were identified throughout the entire study period. Patients infected by non-wild type strains presented prolonged treatment times, needed increased antifungal doses than those described in the literature and one of them presented a permanent sequel. In addition, three of them, with immunosuppression, died from sporotrichosis. Despite the broad use of antifungal drugs in hyperendemic areas of sporotrichosis, an emergence of non-wild type strains did not occur. The results of in vitro antifungal susceptibility tests should guide sporotrichosis therapy, especially in immunosuppressed patients.

Silver Chitosan Nanocomposites are Effective to Combat Sporotrichosis

The use of silver nanoparticles (AgNPs) embedded in polymeric matrix has acquired special attention as a strategy to reduce metal toxicity without losing its antimicrobial effect. In this work, the green synthesis of AgNPs and their functionalization with chitosan (AgNPs@Chi) was performed, and their antifungal activity investigated against the foremost species responsible for causing sporotrichosis, Sporothrix brasiliensis and Sporothrix schenckii. In vitro studies revealed inhibitory concentrations ranging from 0.12–1 μg/ml for both nanocomposites (NCs). Silver release in suspension displayed chitosan as a potential vehicle for continuous silver discharge, with a complete release after 52 days. No synergistic effects were observed in vitro when the NCs were combined with itraconazole or amphotericin B. Treatment of S. brasiliensis with NCs caused morphological deformities, cell membrane discontinuity and an intense cytoplasmic degeneration. Remarkably, both NCs induced the growth and migration of keratinocytes and fibroblasts when compared to control conditions. In addition, functionalization of AgNPs with chitosan significantly reduced its hemolytic activity, suggesting their potential use in vivo. Finally, silver nanocomposites were used as a daily topical treatment in a murine model of subcutaneous sporotrichosis, showing the ability to reduce the Sporothrix infection and stimulate tissue repair. In combination, our results demonstrate that AgNPs@Chi can be a non-toxic and efficient alternative for sporotrichosis.

Treatment of Human Sporotrichosis Caused by Sporothrix brasiliensis

We describe the successful treatment of a series of 30 zoonotic sporotrichosis cases from southern Brazil. Sporothrix brasiliensis was the species genotypically identified in all 25 confirmed cases. Five other cases were classified as probable, without laboratory confirmation, but with clinical and epidemiological data of cat-transmitted sporotrichosis. Two isolates were sequenced by translation elongation factor-1 alpha (EF1α) loci in order to compare their sequences, and both of them showed distinct genotypes from S. brasiliensis strains from other Brazilian states. Itraconazole (ITZ) or potassium iodide (KI) were the first choice treatment in 28 and 2 cases, respectively. Microdilution assay showed a wild-type profile of S. brasiliensis isolates to ITZ. However, a lack of clinical response occurred in 42% of cases, especially those treated with ITZ 100 mg/day, and treatment needed modifications, by either increased doses or antifungal combinations. Clinical cure required a mean of 187 days of treatment, which was dependent on the clinical form of the disease and age of patients. Therapy, including dosages and durations, for cutaneous forms of sporotrichosis requires re-evaluation, since cases caused by S. brasiliensis may influence treatment efficacy.

Antifungal activity of Acylhydrazone derivatives against Sporothrix spp

Sporotrichosis is an emerging mycosis caused by members of the genus Sporothrix The disease affects humans and animals, particularly cats, which plays an important role in the zoonotic transmission. Feline sporotrichosis treatment options include itraconazole (ITC), potassium iodide and amphotericin B, drugs usually associated with deleterious adverse reactions and refractoriness in cats, especially when using ITC. Thus, affordable, non-toxic and clinically effective anti-Sporothrix agents are needed. Recently, acylhydrazones (AH), molecules targeting vesicular transport and cell cycle progression, exhibited a potent antifungal activity against several fungal species and displayed low toxicity when compared to the current drugs. In this work, the AH derivatives D13 and SB-AF-1002 were tested against Sporothrix schenckii and Sporothrix brasiliensis Minimal inhibitory concentrations of 0.12 - 1 μg/mL were observed for both species in vitro D13 and SB-AF-1002 showed an additive effect with itraconazole. Treatment with D13 promoted yeast disruption with release of intracellular components, as confirmed by transmission electron microscopy of S. brasiliensis exposed to the AH derivatives. AH-treated cells displayed thickening of the cell wall, discontinuity of the cell membrane and an intense cytoplasmic degeneration. In a murine model of sporotrichosis, treatment with AH derivatives was more efficient than ITC, the drug of choice for sporotrichosis. The results of the preliminary clinical study in cats indicate that D13 is safe and has potential to become a therapeutic option for sporotrichosis when associated to ITC. Our results expand the antifungal broadness of AH derivatives and suggest that these drugs could be exploited to combat sporotrichosis.

Bone sporotrichosis: 41 cases from a reference hospital in Rio de Janeiro, Brazil

Background

Bone sporotrichosis is rare. The metropolitan region of Rio de Janeiro is hyperendemic for zoonotic sporotrichosis and the bone presentations are increasing.

Methods

We studied a retrospective cohort of 41 cases of bone sporotrichosis, diagnosed from 1999–2016. The inclusion criteria was fungal culture isolation from any clinical specimen associated to bone involvement (radiography and/or computed tomography) compatible with fungal osteomyelitis or histopathological findings of bone material compatible with sporotrichosis. Molecular identification was performed when possible.

Results

Male patients represented 58.5% of the cases, with a cohort median age of 43 years. Immunosuppressive conditions were present in 68.3% of the patients, mostly HIV coinfection (51.2%). Multifocal bone involvement (more than one anatomical segment) was diagnosed in 61% of the patients, while 39% presented unifocal involvement. The bones of the hands were the most affected (58.5%), followed by the feet (41.5%) and tibia (26.8%). Multifocal group was characterized by a higher proportion of males (p = 0.0045) with immunosuppressive conditions (p = 0.0014). Amphotericin B followed by oral itraconazole was the main treatment, with a median time of 16.7 months (1.5 to 99.2 months), and cure of 53.7% of the patients (84.6% of immunocompetent and 39.3% of immunocompromised patients). Sequelae occurred in 12.2% of the patients—amputations (7.3%) and ankylosis (4.9%), while 22% died in the course of the disease. Sporothrix brasiliensis was the causative agent in all the 9 (22%) performed cases.

Conclusions

Bone sporotrichosis is a chronic, challenging condition with prolonged treatment, often with poor results and sequelae.

Sporotrichosis is a subcutaneous mycosis, more common in tropical and subtropical countries, and the involvement of bones is rare. The metropolitan region of Rio de Janeiro is hyperendemic for zoonotic sporotrichosis and the bone presentations are increasing. We evaluated 41 cases of bone sporotrichosis at a reference center in infectious diseases. There was a predominance of men with immunosuppressive conditions, notably HIV infection and alcoholism. Immunosuppression was related to multifocal bone involvement and more severe disease. This form of the disease is a chronic, challenging condition with prolonged treatment, often with poor results and sequelae.

Antifungal resistance on Sporothrix species: an overview

INTRODUCTION

The treatment of human and animal sporotrichosis is often performed with antifungal agents; however, the emergence of antifungal-resistant strains of Sporothrix species has been reported. We aimed to discuss the ability of Sporothrix species in developing resistance to the conventional antifungals and mechanisms for this.

METHODOLOGY

Published data on databases (PubMed, Science Direct, Google Scholar) were investigated using a combination of keywords from 2008 to 2019 by the StArt tool.

RESULTS

The minimal inhibitory concentrations values based on the Clinical and Laboratory Standards Institute (CLSI) from eight references were classified according to the epidemiological cutoff values in wild-type or non-wild-type strains. In this way, non-wild-type S. schenckii and, mainly, S. brasiliensis isolates were recognized on itraconazole, amphotericin B, terbinafine, and voriconazole, which are strains that deserve more attention toward antifungal control, with a probable risk of mutation to antifungal resistance. Among the few reviewed studied on antifungal resistance, the melanin production capacity (DHN-melanin, L-DOPA melanin, and pyomelanin), the low genetic diversity due to the abnormal number of chromosomes, and the mutation in cytochrome P450 are some of the factors for developing resistance mechanism.

CONCLUSIONS

The emergence of Sporothrix species with in vitro antifungal resistance was evidenced and the possible mechanisms for resistance development may be due to the melanin production capacity, genetic diversity and mutations in cytochrome P450. Further studies should be carried out targeting gene expression for the development of antifungal resistance on Sporothrix species in order to prospect new therapeutic targets for human and veterinary use.

Sporothrix Brasiliensis: A Review of an Emerging South American Fungal Pathogen, Its Related Disease, Presentation and Spread in Argentina

Sporotrichosis, caused by Sporothrix schenckii and related species, is the most frequent implantation mycosis in Latin America. In Argentina, over the last 8 years, there have been 0.16 new cases per month of feline sporotrichosis in 2011, increasing to 0.75 cases per month in 2019 and involving zoonotic transmission to humans. Molecular identification by polymerase chain reaction (PCR) detected Sporothrix brasiliensis in these feline and zoonotic outbreaks. This study will focus on different feline and human sporotrichosis outbreaks caused by S. brasiliensis in Argentina during 2011–2019. We will address the sources of infection and environmental hotspots, as well as the application of several treatment strategies for improving the pharmacotherapy of the different clinical forms of the disease. Finally, we will provide a detailed summary of the clinical aspects and new advances in host–pathogen interactions, virulence factors and immune response, focusing on state-of-the-art diagnostic tools and potential vaccine candidates.

Sporotrichosis refractory to conventional treatment: therapeutic success with potassium iodide

Sporotrichosis is a subcutaneous mycosis caused by dimorphic fungi of the genus Sporothrix. The authors report a case of fixed cutaneous sporotrichosis with therapeutic failure after 18 months of itraconazole and terbinafine associated with cryosurgery. The patient was cured after the introduction of saturated potassium iodide solution. Sporothrix brasiliensis was the identified species, presenting a susceptibility profile to itraconazole and terbinafine. This fact suggests that therapeutic failure is probably related to the host-fungus interaction rather than drug resistance. It is possible that the immunomodulatory action of the saturated potassium iodide solution may have played an important role in curing this patient.

A novel Sporothrix brasiliensis genomic variant in Midwestern Brazil: evidence for an older and wider sporotrichosis epidemic

Sporotrichosis is a subcutaneous infection caused by fungi from the genus Sporothrix. It is transmitted by inoculation of infective particles found in plant-contaminated material or diseased animals, characterizing the classic sapronotic and emerging zoonotic transmission, respectively. Since 1998, southeastern Brazil has experienced a zoonotic sporotrichosis epidemic caused by S. brasiliensis, centred in the state of Rio de Janeiro. Our observation of feline sporotrichosis cases in Brasília (Midwestern Brazil), around 900 km away from Rio de Janeiro, led us to question whether the epidemic caused by S. brasiliensis has spread from the epicentre in Rio de Janeiro, emerged independently in the two locations, or if the disease has been present and unrecognized in Midwestern Brazil. A retrospective analysis of 91 human and 4 animal cases from Brasília, ranging from 1993 to 2018, suggests the occurrence of both sapronotic and zoonotic transmission. Molecular typing of the calmodulin locus identified S. schenckii as the agent in two animals and all seven human patients from which we were able to recover clinical isolates. In two other animals, the disease was caused by S. brasiliensis. Whole-genome sequence typing of seven Sporothrix spp. strains from Brasília and Rio de Janeiro suggests that S. brasiliensis isolates from Brasília are genetically distinct from those obtained at the epicentre of the outbreak in Rio de Janeiro, both in phylogenomic and population genomic analyses. The two S. brasiliensis populations seem to have separated between 2.2 and 3.1 million years ago, indicating independent outbreaks or that the zoonotic S. brasiliensis outbreak might have started earlier and be more widespread in South America than previously recognized.

Evolution of virulence-related phenotypes of Sporothrix brasiliensis isolates from patients with chronic sporotrichosis and acquired immunodeficiency syndrome

Sporotrichosis in immunocompromised patients has a high morbidity and may cause deaths. Particularly, patients with acquired immunodeficiency syndrome (AIDS) with low T CD4 counts develop a chronic disease, with severe and widespread forms. Recently, the ability of Sporothrix brasiliensis, the main agent of zoonotic sporotrichosis, to increase its virulence in a diabetic patient without HIV infection was described. Since it was a unique finding, it is not known how often this occurs in patients with chronic and refractory sporotrichosis. The aim of this study is to compare sequential Sporothrix isolates obtained from patients with sporotrichosis and AIDS in order to detect changes in virulence-related phenotypes and acquisition of antifungal resistance during the evolution of the disease. Fungal growth in different substrates, antifungal susceptibility, thermotolerance, resistance to oxidative stress, and production of hydrolytic enzymes were evaluated. Correlations were assessed between clinical and phenotypic variables. Sixteen isolates, all identified as S. brasiliensis, obtained from five patients were studied. They grew well on glucose and N-acetyl-D-glucosamine, but poorly on lactate. Except from isolates collected from two patients, which were non-wild type for terbinafine, they were considered wild type for the antifungal drugs tested. Thermotolerance of the isolates was moderate to high. Except for phytase and phospholipase, isolates were able to produce virulence-related enzymes on different levels. Changes in all studied phenotypes were observed during the course of the disease in some patients. The results show that the HIV-driven immunosuppression is more relevant than fungal phenotypes on the unfavorable outcomes of disseminated sporotrichosis.

Immunopathogenesis of Human Sporotrichosis: What We Already Know

Sporotrichosis is a subacute/chronic mycosis caused by dimorphic fungus of the genus Sporothrix. This mycosis may affect both human and domestic animals and in the last few years, the geographic dispersion and increase of sporotrichosis worldwide has been observed. The occurrence of cases related to scratching/bites of domestic felines have increased, characterizing the disease as predominantly a zoonosis. In humans, sporotrichosis mainly involves the cutaneous tegument of infected patients, but other tissues may also present the infection. The main forms of clinical presentation are lymphocutanous sporotrichosis (LC) and fixed sporotrichosis (F). Although less common, mucosal, cutaneous disseminated, and extracutaneous forms have also been described. Multiple factors from the fungus and host can play a role in driving the clinical evolution of sporotrichosis to benign or severe disease. In this review, we discuss the immunopathological aspects involved in human sporotrichosis. Putting together the two branches of knowledge—host immune response and fungal evading mechanisms—we may perceive new possibilities in understanding the fungus–host interaction in order to be in a position to go further in the control of sporotrichosis.

Cryosurgery for the treatment of cutaneous sporotrichosis in four pregnant women

Background

Pregnant women with sporotrichosis should not receive systemic antifungal therapy except in severe cases when amphotericin B is recommended. Thermotherapy is the most reported treatment described in this group of patients. It entails weeks of daily self-application of heat to the lesions, requires that the patient faithfully apply it, and it could cause skin burns. Cryosurgery is a useful therapeutic tool for many cutaneous infectious diseases, safe for pregnant women, but not well evaluated for sporotrichosis treatment in this group.

Methodology

The authors conducted a retrospective study describing epidemiological, clinical, and therapeutic data related to four pregnant patients with sporotrichosis treated with cryosurgery. The authors reviewed the clinical records of four pregnant patients diagnosed with cutaneous sporotrichosis and treated with cryosurgery. The sessions were carried out monthly up to clinical cure. Molecular identification of the Sporothrix species was performed in two cases using T3B PCR fingerprinting assays.

Principal findings

All patients were in the second trimester of pregnancy and their age ranged from 18 to 34 years. With regard to clinical presentation, two patients had lymphocutaneous and two had the fixed form. S. brasiliensis was identified in two cases as the causative agent. Cryosurgery was well tolerated and the number of sessions ranged from 1 to 3. All the patients reached a complete clinical cure.

Conclusions

Cryosurgery was a safe, easy to perform and well tolerated method, and therefore it is suggested to be a suitable option for the treatment of cutaneous sporotrichosis in pregnant women.

Sporotrichosis is a cosmopolitan disease, considered the most important subcutaneous mycosis in Latin America. Since 1998, there is an ongoing cat-transmitted zoonotic epidemic of sporotrichosis occurring in Rio de Janeiro, Brazil. Pregnant women are a vulnerable population occasionally affected that require special attention regarding sporotrichosis treatment. Antifungal drugs should be avoided because of their potential risks to the fetus, unless in severe cases when amphotericin B (an intravenous antifungal drug) can be indicated. In this context, local measures are the treatment of choice. Cryosurgery consists in local application of intense cold using liquid nitrogen to destroy some infectious, tumoral and inflammatory cutaneous diseases. It is scarcely reported in the literature for the treatment of sporotrichosis, especially in pregnant women for whom local heat is most used. This works aims to describe the clinical response and outcome of cryosurgery for the treatment of sporotrichosis in four pregnant women. All patients reached clinical cure after one to three sessions. These results suggest that cryosurgery can be a well-tolerated, safe, and efficient method for the treatment of sporotrichosis in pregnancy.

Multicenter, International Study of MIC/MEC Distributions for Definition of Epidemiological Cutoff Values for Sporothrix Species Identified by Molecular Methods

Clinical and Laboratory Standards Institute (CLSI) conditions for testing the susceptibilities of pathogenic Sporothrix species to antifungal agents are based on a collaborative study that evaluated five clinically relevant isolates of Sporothrixschenckii sensu lato and some antifungal agents. With the advent of molecular identification, there are two basic needs: to confirm the suitability of these testing conditions for all agents and Sporothrix species and to establish species-specific epidemiologic cutoff values (ECVs) or breakpoints (BPs) for the species. We collected available CLSI MICs/minimal effective concentrations (MECs) of amphotericin B, five triazoles, terbinafine, flucytosine, and caspofungin for 301 Sporothrix schenckii sensu stricto, 486 S. brasiliensis, 75 S. globosa, and 13 S. mexicana molecularly identified isolates. Data were obtained in 17 independent laboratories (Australia, Europe, India, South Africa, and South and North America) using conidial inoculum suspensions and 48 to 72 h of incubation at 35°C. Sufficient and suitable data (modal MICs within 2-fold concentrations) allowed the proposal of the following ECVs for S. schenckii and S. brasiliensis, respectively: amphotericin B, 4 and 4 μg/ml; itraconazole, 2 and 2 μg/ml; posaconazole, 2 and 2 μg/ml; and voriconazole, 64 and 32 μg/ml. Ketoconazole and terbinafine ECVs for S. brasiliensis were 2 and 0.12 μg/ml, respectively. Insufficient or unsuitable data precluded the calculation of ketoconazole and terbinafine (or any other antifungal agent) ECVs for S. schenckii, as well as ECVs for S. globosa and S. mexicana These ECVs could aid the clinician in identifying potentially resistant isolates (non-wild type) less likely to respond to therapy.

Minimal inhibitory concentration distributions and epidemiological cutoff values of five antifungal agents against Sporothrix brasiliensis

BACKGROUND

Sporothrix brasiliensis is the most virulent sporotrichosis agent. This species usually responds to antifungal drugs, but therapeutic failure can occur in some patients. Antifungal susceptibility tests have been performed on this species, but no clinical breakpoints (CBPs) are available. In this situation, minimal inhibitory concentration (MIC) distributions and epidemiological cutoff values (ECVs) support the detection of identification of resistant strains.

OBJECTIVES

To study the MIC distributions of five antifungal drugs against S. brasiliensis and to propose tentative ECVs.

METHODS

MICs of amphotericin B (AMB), itraconazole (ITR), ketoconazole (KET), posaconazole (POS), and terbinafine (TRB) against 335 S. brasiliensis strains were determined by the Clinical and Laboratory Standards Institute broth microdilution method.

FINDINGS

The proposed ECV, in µg/mL, for AMB, ITR, KET, POS, and TRB were 4.0, 2.0, 1.0, 2.0, and 0.25, respectively. Percentages of wild-type strains in our population for the above antifungal drugs were 98.48, 95.22, 95.33, 100, and 97.67%, respectively.

MAIN CONCLUSIONS

These ECVs will be useful to detect strains with resistance, to define CBPs, and to elaborate specific therapeutic guidelines for S. brasiliensis. Rational use of antifungals is strongly recommended to avoid the emergence of resistant strains and ensure the therapeutic effectiveness of sporotrichosis.